1 /*
2 * Debug helper to dump the current kernel pagetables of the system
3 * so that we can see what the various memory ranges are set to.
4 *
5 * (C) Copyright 2008 Intel Corporation
6 *
7 * Author: Arjan van de Ven <arjan@linux.intel.com>
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * as published by the Free Software Foundation; version 2
12 * of the License.
13 */
14
15 #include <linux/debugfs.h>
16 #include <linux/mm.h>
17 #include <linux/module.h>
18 #include <linux/seq_file.h>
19
20 #include <asm/pgtable.h>
21
22 /*
23 * The dumper groups pagetable entries of the same type into one, and for
24 * that it needs to keep some state when walking, and flush this state
25 * when a "break" in the continuity is found.
26 */
27 struct pg_state {
28 int level;
29 pgprot_t current_prot;
30 unsigned long start_address;
31 unsigned long current_address;
32 const struct addr_marker *marker;
33 unsigned long lines;
34 bool to_dmesg;
35 };
36
37 struct addr_marker {
38 unsigned long start_address;
39 const char *name;
40 unsigned long max_lines;
41 };
42
43 /* indices for address_markers; keep sync'd w/ address_markers below */
44 enum address_markers_idx {
45 USER_SPACE_NR = 0,
46 #ifdef CONFIG_X86_64
47 KERNEL_SPACE_NR,
48 LOW_KERNEL_NR,
49 VMALLOC_START_NR,
50 VMEMMAP_START_NR,
51 # ifdef CONFIG_X86_ESPFIX64
52 ESPFIX_START_NR,
53 # endif
54 HIGH_KERNEL_NR,
55 MODULES_VADDR_NR,
56 MODULES_END_NR,
57 #else
58 KERNEL_SPACE_NR,
59 VMALLOC_START_NR,
60 VMALLOC_END_NR,
61 # ifdef CONFIG_HIGHMEM
62 PKMAP_BASE_NR,
63 # endif
64 FIXADDR_START_NR,
65 #endif
66 };
67
68 /* Address space markers hints */
69 static struct addr_marker address_markers[] = {
70 { 0, "User Space" },
71 #ifdef CONFIG_X86_64
72 { 0x8000000000000000UL, "Kernel Space" },
73 { PAGE_OFFSET, "Low Kernel Mapping" },
74 { VMALLOC_START, "vmalloc() Area" },
75 { VMEMMAP_START, "Vmemmap" },
76 # ifdef CONFIG_X86_ESPFIX64
77 { ESPFIX_BASE_ADDR, "ESPfix Area", 16 },
78 # endif
79 { __START_KERNEL_map, "High Kernel Mapping" },
80 { MODULES_VADDR, "Modules" },
81 { MODULES_END, "End Modules" },
82 #else
83 { PAGE_OFFSET, "Kernel Mapping" },
84 { 0/* VMALLOC_START */, "vmalloc() Area" },
85 { 0/*VMALLOC_END*/, "vmalloc() End" },
86 # ifdef CONFIG_HIGHMEM
87 { 0/*PKMAP_BASE*/, "Persisent kmap() Area" },
88 # endif
89 { 0/*FIXADDR_START*/, "Fixmap Area" },
90 #endif
91 { -1, NULL } /* End of list */
92 };
93
94 /* Multipliers for offsets within the PTEs */
95 #define PTE_LEVEL_MULT (PAGE_SIZE)
96 #define PMD_LEVEL_MULT (PTRS_PER_PTE * PTE_LEVEL_MULT)
97 #define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
98 #define PGD_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
99
100 #define pt_dump_seq_printf(m, to_dmesg, fmt, args...) \
101 ({ \
102 if (to_dmesg) \
103 printk(KERN_INFO fmt, ##args); \
104 else \
105 if (m) \
106 seq_printf(m, fmt, ##args); \
107 })
108
109 #define pt_dump_cont_printf(m, to_dmesg, fmt, args...) \
110 ({ \
111 if (to_dmesg) \
112 printk(KERN_CONT fmt, ##args); \
113 else \
114 if (m) \
115 seq_printf(m, fmt, ##args); \
116 })
117
118 /*
119 * Print a readable form of a pgprot_t to the seq_file
120 */
printk_prot(struct seq_file * m,pgprot_t prot,int level,bool dmsg)121 static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
122 {
123 pgprotval_t pr = pgprot_val(prot);
124 static const char * const level_name[] =
125 { "cr3", "pgd", "pud", "pmd", "pte" };
126
127 if (!pgprot_val(prot)) {
128 /* Not present */
129 pt_dump_cont_printf(m, dmsg, " ");
130 } else {
131 if (pr & _PAGE_USER)
132 pt_dump_cont_printf(m, dmsg, "USR ");
133 else
134 pt_dump_cont_printf(m, dmsg, " ");
135 if (pr & _PAGE_RW)
136 pt_dump_cont_printf(m, dmsg, "RW ");
137 else
138 pt_dump_cont_printf(m, dmsg, "ro ");
139 if (pr & _PAGE_PWT)
140 pt_dump_cont_printf(m, dmsg, "PWT ");
141 else
142 pt_dump_cont_printf(m, dmsg, " ");
143 if (pr & _PAGE_PCD)
144 pt_dump_cont_printf(m, dmsg, "PCD ");
145 else
146 pt_dump_cont_printf(m, dmsg, " ");
147
148 /* Bit 9 has a different meaning on level 3 vs 4 */
149 if (level <= 3) {
150 if (pr & _PAGE_PSE)
151 pt_dump_cont_printf(m, dmsg, "PSE ");
152 else
153 pt_dump_cont_printf(m, dmsg, " ");
154 } else {
155 if (pr & _PAGE_PAT)
156 pt_dump_cont_printf(m, dmsg, "pat ");
157 else
158 pt_dump_cont_printf(m, dmsg, " ");
159 }
160 if (pr & _PAGE_GLOBAL)
161 pt_dump_cont_printf(m, dmsg, "GLB ");
162 else
163 pt_dump_cont_printf(m, dmsg, " ");
164 if (pr & _PAGE_NX)
165 pt_dump_cont_printf(m, dmsg, "NX ");
166 else
167 pt_dump_cont_printf(m, dmsg, "x ");
168 }
169 pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
170 }
171
172 /*
173 * On 64 bits, sign-extend the 48 bit address to 64 bit
174 */
normalize_addr(unsigned long u)175 static unsigned long normalize_addr(unsigned long u)
176 {
177 #ifdef CONFIG_X86_64
178 return (signed long)(u << 16) >> 16;
179 #else
180 return u;
181 #endif
182 }
183
184 /*
185 * This function gets called on a break in a continuous series
186 * of PTE entries; the next one is different so we need to
187 * print what we collected so far.
188 */
note_page(struct seq_file * m,struct pg_state * st,pgprot_t new_prot,int level)189 static void note_page(struct seq_file *m, struct pg_state *st,
190 pgprot_t new_prot, int level)
191 {
192 pgprotval_t prot, cur;
193 static const char units[] = "BKMGTPE";
194
195 /*
196 * If we have a "break" in the series, we need to flush the state that
197 * we have now. "break" is either changing perms, levels or
198 * address space marker.
199 */
200 prot = pgprot_val(new_prot) & PTE_FLAGS_MASK;
201 cur = pgprot_val(st->current_prot) & PTE_FLAGS_MASK;
202
203 if (!st->level) {
204 /* First entry */
205 st->current_prot = new_prot;
206 st->level = level;
207 st->marker = address_markers;
208 st->lines = 0;
209 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
210 st->marker->name);
211 } else if (prot != cur || level != st->level ||
212 st->current_address >= st->marker[1].start_address) {
213 const char *unit = units;
214 unsigned long delta;
215 int width = sizeof(unsigned long) * 2;
216
217 /*
218 * Now print the actual finished series
219 */
220 if (!st->marker->max_lines ||
221 st->lines < st->marker->max_lines) {
222 pt_dump_seq_printf(m, st->to_dmesg,
223 "0x%0*lx-0x%0*lx ",
224 width, st->start_address,
225 width, st->current_address);
226
227 delta = st->current_address - st->start_address;
228 while (!(delta & 1023) && unit[1]) {
229 delta >>= 10;
230 unit++;
231 }
232 pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
233 delta, *unit);
234 printk_prot(m, st->current_prot, st->level,
235 st->to_dmesg);
236 }
237 st->lines++;
238
239 /*
240 * We print markers for special areas of address space,
241 * such as the start of vmalloc space etc.
242 * This helps in the interpretation.
243 */
244 if (st->current_address >= st->marker[1].start_address) {
245 if (st->marker->max_lines &&
246 st->lines > st->marker->max_lines) {
247 unsigned long nskip =
248 st->lines - st->marker->max_lines;
249 pt_dump_seq_printf(m, st->to_dmesg,
250 "... %lu entr%s skipped ... \n",
251 nskip,
252 nskip == 1 ? "y" : "ies");
253 }
254 st->marker++;
255 st->lines = 0;
256 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
257 st->marker->name);
258 }
259
260 st->start_address = st->current_address;
261 st->current_prot = new_prot;
262 st->level = level;
263 }
264 }
265
walk_pte_level(struct seq_file * m,struct pg_state * st,pmd_t addr,unsigned long P)266 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
267 unsigned long P)
268 {
269 int i;
270 pte_t *start;
271
272 start = (pte_t *) pmd_page_vaddr(addr);
273 for (i = 0; i < PTRS_PER_PTE; i++) {
274 pgprot_t prot = pte_pgprot(*start);
275
276 st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
277 note_page(m, st, prot, 4);
278 start++;
279 }
280 }
281
282 #if PTRS_PER_PMD > 1
283
walk_pmd_level(struct seq_file * m,struct pg_state * st,pud_t addr,unsigned long P)284 static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
285 unsigned long P)
286 {
287 int i;
288 pmd_t *start;
289
290 start = (pmd_t *) pud_page_vaddr(addr);
291 for (i = 0; i < PTRS_PER_PMD; i++) {
292 st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
293 if (!pmd_none(*start)) {
294 pgprotval_t prot = pmd_val(*start) & PTE_FLAGS_MASK;
295
296 if (pmd_large(*start) || !pmd_present(*start))
297 note_page(m, st, __pgprot(prot), 3);
298 else
299 walk_pte_level(m, st, *start,
300 P + i * PMD_LEVEL_MULT);
301 } else
302 note_page(m, st, __pgprot(0), 3);
303 start++;
304 }
305 }
306
307 #else
308 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
309 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
310 #define pud_none(a) pmd_none(__pmd(pud_val(a)))
311 #endif
312
313 #if PTRS_PER_PUD > 1
314
walk_pud_level(struct seq_file * m,struct pg_state * st,pgd_t addr,unsigned long P)315 static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
316 unsigned long P)
317 {
318 int i;
319 pud_t *start;
320
321 start = (pud_t *) pgd_page_vaddr(addr);
322
323 for (i = 0; i < PTRS_PER_PUD; i++) {
324 st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
325 if (!pud_none(*start)) {
326 pgprotval_t prot = pud_val(*start) & PTE_FLAGS_MASK;
327
328 if (pud_large(*start) || !pud_present(*start))
329 note_page(m, st, __pgprot(prot), 2);
330 else
331 walk_pmd_level(m, st, *start,
332 P + i * PUD_LEVEL_MULT);
333 } else
334 note_page(m, st, __pgprot(0), 2);
335
336 start++;
337 }
338 }
339
340 #else
341 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(pgd_val(a)),p)
342 #define pgd_large(a) pud_large(__pud(pgd_val(a)))
343 #define pgd_none(a) pud_none(__pud(pgd_val(a)))
344 #endif
345
ptdump_walk_pgd_level(struct seq_file * m,pgd_t * pgd)346 void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
347 {
348 #ifdef CONFIG_X86_64
349 pgd_t *start = (pgd_t *) &init_level4_pgt;
350 #else
351 pgd_t *start = swapper_pg_dir;
352 #endif
353 int i;
354 struct pg_state st = {};
355
356 if (pgd) {
357 start = pgd;
358 st.to_dmesg = true;
359 }
360
361 for (i = 0; i < PTRS_PER_PGD; i++) {
362 st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
363 if (!pgd_none(*start)) {
364 pgprotval_t prot = pgd_val(*start) & PTE_FLAGS_MASK;
365
366 if (pgd_large(*start) || !pgd_present(*start))
367 note_page(m, &st, __pgprot(prot), 1);
368 else
369 walk_pud_level(m, &st, *start,
370 i * PGD_LEVEL_MULT);
371 } else
372 note_page(m, &st, __pgprot(0), 1);
373
374 start++;
375 }
376
377 /* Flush out the last page */
378 st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
379 note_page(m, &st, __pgprot(0), 0);
380 }
381
ptdump_show(struct seq_file * m,void * v)382 static int ptdump_show(struct seq_file *m, void *v)
383 {
384 ptdump_walk_pgd_level(m, NULL);
385 return 0;
386 }
387
ptdump_open(struct inode * inode,struct file * filp)388 static int ptdump_open(struct inode *inode, struct file *filp)
389 {
390 return single_open(filp, ptdump_show, NULL);
391 }
392
393 static const struct file_operations ptdump_fops = {
394 .open = ptdump_open,
395 .read = seq_read,
396 .llseek = seq_lseek,
397 .release = single_release,
398 };
399
pt_dump_init(void)400 static int pt_dump_init(void)
401 {
402 struct dentry *pe;
403
404 #ifdef CONFIG_X86_32
405 /* Not a compile-time constant on x86-32 */
406 address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
407 address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
408 # ifdef CONFIG_HIGHMEM
409 address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
410 # endif
411 address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
412 #endif
413
414 pe = debugfs_create_file("kernel_page_tables", 0600, NULL, NULL,
415 &ptdump_fops);
416 if (!pe)
417 return -ENOMEM;
418
419 return 0;
420 }
421
422 __initcall(pt_dump_init);
423 MODULE_LICENSE("GPL");
424 MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
425 MODULE_DESCRIPTION("Kernel debugging helper that dumps pagetables");
426